1. Field of the Invention
The present invention relates, in general, to data storage and back-up solutions for recovering data existing at a particular point in time, such as after a system crash, and, more particularly, to software, hardware and systems, and methods for providing continuous data protection in a manner that allows a user or customer to obtain a copy of information or stored data from a selected point of time.
2. Relevant Background
In the data storage industries, the need for effective and reliable backup and archive of data or information is well known. Today's businesses and other institutions are devoting a significant amount of time and money toward information system (IS) resources that are devoted to providing backup and archive of information resident in computers and servers within their organizations that produce and rely upon digital information. The customers of the data storage industry are more frequently demanding that not only is their data properly backed up but also that when needed, such as after a system failure that causes a loss of data, that the backed up data be accessible at a particular point in time. In other words, there is an increasing demand for continuous data protection that allows data to be restored back to its state at a particular moment in time, which is most commonly a point in time just before their computer or data storage system crashed or was lost. The demand for continuous data protection, though, must also be balanced against the demand for low data storage costs and for speed in processing data.
Today, the term “backup” generally means that periodically, such as each day, a backup record is made that mirrors then-present information in active memory and storage of a computer or computer server. This backup operation usually involves a transfer of data to disk storage, such as to a redundant array of inexpensive disks (RAID) system, and/or to magnetic tape. The backup operation often occurs during a period of likely minimum usage of the active memory and/or data storage (or data storage resources), such as in the middle of the night. If the storage resource is thereafter lost or becomes unavailable on account of equipment failure, or for any other reason (e.g., a virus strikes at noon or a personnel error causes a crash), it is then possible to use the backup record to reconstruct the state of the information in storage as of the last backup time and date.
For many users, it is unacceptable to not be able to go back to a time immediately before the loss of the storage resource, which may mean the loss of a days or at least several hours of stored data changes (e.g., want to go back to a minute or even seconds before the virus hit or personnel mistake occurred). Unfortunately, only a limited number of alternatives have been available to the common point-in-time backup method for protecting data. Some of the solutions directed to providing continuous data protection (or “CDP”) have been very complex and have required significant software and/or hardware modifications to existing systems. This has generally resulted in customers refusing to implement such CDP solutions as being too expensive or complex, host specific, or processor hungry, and instead, these users go forward relying on existing periodic backup possibly with more frequent point-in-time backups of their data as the only improvement.
As a result, existing backup solutions including existing CDP techniques do not meet the needs of data storage customers, and there is a continuing need for enhanced techniques for providing continuous or near continuous data protection. Such techniques preferably can be implemented using existing data storage hardware with only limited increases in their operating complexities, with minimal changes in their processing speeds, and at costs that are more acceptable to data storage users.